1. Field of the Invention
This invention relates generally to the field of semiconductor device manufacturing and, more particularly, to a method and apparatus for implementing dynamic qualification recipes.
2. Description of the Invention
There is a constant drive within the semiconductor industry to increase the quality, reliability and throughput of integrated circuit devices, e.g., microprocessors, memory devices, and the like. This drive is fueled by consumer demands for higher quality computers and electronic devices that operate more reliably. These demands have resulted in a continual improvement in the manufacture of semiconductor devices, e.g., transistors, as well as in the manufacture of integrated circuit devices incorporating such transistors. Additionally, reducing the defects in the manufacture of the components of a typical transistor also lowers the overall cost per transistor as well as the cost of integrated circuit devices incorporating such transistors.
Generally, a set of processing steps is performed on a lot of wafers using a variety of process tools, including photolithography steppers, etch tools, deposition tools, polishing tools, rapid thermal process tools, implantation tools, etc. The technologies underlying semiconductor process tools have attracted increased attention over the last several years, resulting in substantial refinements. However, despite the advances made in this area, many of the process tools that are currently commercially available suffer certain deficiencies. In particular, such tools often lack advanced process data monitoring capabilities, such as the ability to provide historical parametric data in a user-friendly format, as well as event logging, real-time graphical display of both current processing parameters and the processing parameters of the entire run, and remote, i.e., local site and worldwide, monitoring. These deficiencies can engender non-optimal control of critical processing parameters, such as throughput, accuracy, stability and repeatability, processing temperatures, mechanical tool parameters, and the like. This variability manifests itself as within-run disparities, run-to-run disparities and tool-to-tool disparities that can propagate into deviations in product quality and performance, whereas an ideal monitoring and diagnostics system for such tools would provide a means of monitoring this variability, as well as providing means for optimizing control of critical parameters.
One technique for improving the operation of semiconductor processing line includes using a factory wide control system to automatically control the operation of the various process tools. The manufacturing tools communicate with a manufacturing framework or a network of processing modules. Each manufacturing tool is generally connected to an equipment interface. The equipment interface is connected to a machine interface which facilitates communications between the manufacturing tool and the manufacturing framework. The machine interface can generally be part of an advanced process control (APC) system. The APC system initiates a control script based upon a manufacturing model, which can be a software program that automatically retrieves the data needed to execute a manufacturing process. Often, semiconductor devices are staged through multiple manufacturing tools for multiple processes, generating data relating to the quality of the processed semiconductor devices.
Various tools in the processing line are controlled in accordance with performance models to reduce processing variation. Commonly controlled tools include photolithography steppers, polishing tools, etching tools, and deposition tools. Pre-processing and/or post-processing metrology data is supplied to process controllers for the tools. Operating recipe parameters, such as processing time, are calculated by the process controllers based on the performance model and the metrology information to attempt to achieve post-polishing results as close to a target value as possible. Reducing variation in this manner leads to increased throughput, reduced cost, higher device performance, etc., all of which equate to increased profitability.
One input to commonly used control models is the xe2x80x9ccurrent statexe2x80x9d of the process tool. The xe2x80x9ccurrent statexe2x80x9d represents the current set of operating parameters associated with the controlled tool. Over time, the state of the process tool may change. For example, as consumable items employed in the process tool deplete, the processing rate of the tool typically changes. Also, as a tool processes wafers, byproducts can build up in the processing chamber, affecting the state. Commonly, a process tool undergoes periodic preventative maintenance procedures or calibrations to keep the tool in optimum operating condition. For example, polishing tools include polishing pads that are periodically conditioned or replaced. Etch tools and deposition tools are periodically cleaned using both in situ cleans or complete disassembly cleans. Steppers are periodically calibrated to maintain alignment accuracy and exposure dose consistency.
Periodically, qualification recipes are performed on the tools, such as after a PM activity or an idle period, to gather information concerning the current state of the tool. These qualification recipes typically employ test wafers. The test wafers are measured after performance of the qualification recipe to determine the state of the tool. Exemplary state information for various tools includes deposition rate, polish rate, polish profile, etch rate, overlay error, etc. Typically, qualification recipes have fixed operating parameters for the tool. For example, a commonly used polishing tool includes concentric rings, each having an individual pressure setting, that apply force to the polishing surface that interfaces with the wafer being polished. The pressure settings affect the polishing rate of the polish tool and also the polishing profile (i.e., dished or domed profile). A typical qualification recipe provides a fixed set of pressure parameters. The thickness of a process layer formed on the test wafer is measured after the polishing operation to determine the blanket wafer removal rate and the polishing profile.
Over time, the state of a polishing tool may change due to changes in the slurry concentration, age of the polishing pads, effectiveness of the conditioning pad, age of the carrier, etc. During normal operation, the operating parameters of the polish tool are changed to account for these sources of variation. Often, the current state of the tool (i.e., evidenced by its current operating parameters) is different than what is tested by the qualification recipe. Accordingly, the information gathered through the performance of the qualification recipe may have reduced relevance to the current state of the tool. If the control model for the tool is initialized using the state information from the qualification procedure, the effectiveness of the process controller attempting to control the characteristics of the processed wafers may be reduced, at least in the short run. It may take a while for the controller to readjust to the sources of variation present in the tool and settle out at a stable state. The need for this settling out time reduces the effectiveness of the process control activities, and thus, tends to increase variation in the manufactured products. Increased variation generally equates to reduced profitability.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
One aspect of the present invention is seen in a method including retrieving current state information associated with a process tool. A dynamic qualification recipe is generated based on the current state information. The dynamic qualification recipe is provided to the process tool for subsequent processing of at least one test workpiece.
Another aspect of the present invention is seen in a system including a process tool and a qualification recipe controller. The qualification recipe controller is configured to retrieve current state information associated with the process tool, generate a dynamic qualification recipe based on the current state information, and provide the dynamic qualification recipe to the process tool for subsequent processing of at least one test workpiece.